The present invention relates to a portable radio device and, more particularly, a portable radio device which receives power from a car adaptor and can transmit/receive a transmission/reception signal.
A conventional radio device is used at various locations because it is compact and light-weight, and can be easily carried. When the radio device is used in an automobile, the radio device can perform radio communication with a distant station at a high output level by using a mobile antenna arranged on the automobile. For this reason, the portable radio device may use the mobile antenna. The portable radio device may be used such that the portable radio device is connected to the car adaptor to receive power from the car adaptor.
FIG. 5 shows an example of the above conventional portable radio device. Referring to FIG. 5, a portable radio device 10 is connected to a car adaptor 11 through a curled cord 12, and a connector 13 connected to the other end of the curled cord 12 having one end connected to the car adaptor 11 is inserted in a predetermined position of the portable radio device 10 and connected thereto. The car adaptor 11 is fixed at a predetermined position in the room of an automobile and connected to an external antenna (not shown) arranged outside the automobile through a high-frequency line 14, and the car adaptor 11 is connected to a car battery (not shown) through a power supply line 15.
In this manner, the portable radio device 10 receives power from the car adaptor 11 through the curled cord 12 and the connector 13 and can perform radio communication using the external antenna through the curled cord 12, the connector 13, and the car adaptor 11. In addition, the portable radio device 10 can be freely moved within an area where the curled cord 12 can extend. Therefore, the portable radio device 10 functions as a telephone transceiver connected to the external antenna through the curled cord 12.
FIG. 6 shows another conventional portable radio device. The same reference numerals as in FIG. 5 denote the same parts in FIG. 6, and a description thereof will be omitted. Referring to FIG. 6, a portable radio device 10 is mounted on a car adaptor 16, and the internal circuit of the portable radio device 10 is used except for its telephone transceiver unit. The car adaptor 16 is fixed at a predetermined position in an automobile room and connected to a telephone transceiver 18 through a curled cord 17.
More specifically, the conventional portable radio device 10 receives power through the car adaptor 16, and can perform radio communication using an external antenna and including a signal process, as in the prior art in FIG. 5. However, in the prior art in FIG. 6, unlike the portable radio device in FIG. 5, the telephone transceiver 18 is arranged for the car adaptor 16, and speech communication with a distant subscriber is performed using the telephone transceiver 18 through the curled cord 17.
However, although the conventional portable radio device shown in FIG. 5 uses the curled cord 12 to obtain a high degree of freedom in an operation, a transmission or reception signal is considerably attenuated when the signal is transmitted through the curled cord 12, and the reception sensitivity of the portable radio device decreases due to attenuation of a reception signal from the external antenna. In addition, the output level of a signal transmitted from the external antenna decreases.
According to the conventional portable radio device shown in FIG. 6, since the portable radio device itself is mounted on the car adaptor 16 without a curled cord, attenuation of a transmission/reception signal caused by the curled cord does not occur. However, the telephone transceiver 18 for speech communication in an automobile is required in addition to the portable radio device. For this reason, the cost increases by the telephone transceiver 18, and a space is required for storing the telephone transceiver 18. Therefore, use of the portable radio device in the limited space of the automobile poses a problem.